Simplified heavy metal staining techniques demonstrated with Fast Plant leaf tissue

Fast Plant(Brassica rapa,Cruciferae)leaf tissuefixed in glutaraldehyde-acrolein and post-fixed in os-mium,was examined for response to several easily-prepared heavy metal stains.Lead and uranium,separately and in combination,gave typical resultsacross the spectrum of cell organellets.As a single stainfollowing osmium,bismuth produced images seeminglyequivalent to lead and uranium.Phosphotungstic acidproduced very good membrane delineation but produceda washed-out background image similar to that from leadstaining.Carbohydrate compounds were especiallyresponsive to ruthenium;the cytoplasm and the matrixof all organelles were also stained very well.Theprocedures were no more demanding than traditionalstaining methods and may be easily used in research andteaching.Fast Plant materials are a reliable,quick andeasy source of living material.     

Effects of Pinealectomy and Ocular Enucleation on Diurnal Periodicity of Leucocytozoon smithi (Haemosporina) Gametocytes in the Peripheral Blood of Domestic Turkeys1

ABSTRACT. Domestic turkeys naturally infected with Leucocytozoon smithi were blinded by bilateral ocular enucleation, pinealectomized, sham-pinealectomized, pinealectomized plus enucleated, or maintained as controls. Groups of turkeys were acclimated to either light-dark periods of 14L:10D or “darkness” with intermittent periods (10–20 min) of red light at irregular hours approximately every three days as required for maintenance of turkeys. Peripheral gametocyte numbers of L. smithi in all groups were determined every 2 h over a 36 h period. Under 14L: 10D photoperiod, no observable difference in the pattern of gametocyte circadian rhythmicity between pinealectomized, enucleated, pinealectomized plus enucleated, and control turkeys was noted. Although mean parasitemias differed among groups, peak gametocyte numbers occurred between 1000 and 1800 h; how parasitemias occurred between 2000 and 0400 h. However, the phase of gametocyte rhythmicity in pinealectomized plus enucleated turkey hosts did exhibit a lag with reference to other hosts when examined by least squares fits of simple harmonics. Under conditions of “darkness” with intermittent, irregular periods of red light, L. smithi gametocyte numbers of individual turkeys, pinealectomized, sham-pinealectomized, or maintained as controls, exhibited a circadian periodicity though parasite cycles were out of phase with the natural photoperiod to which the turkeys previously had been exposed. A slight drift out of phase of L. smithi gametocyte periodicity occurred among turkeys in the sham-pinealectomized and the control groups while a considerably more prominent drift out of phase was seen among the parasite rhythmicity patterns of the pinealectomized birds. Data indicate that the pineal gland of the turkey did not directly mediate L. smithi gametocyte circadian periodicity, although an indirect involvement in regulating the timing of parasite rhythmicity is suggested.     

Development of multiple dominant markers by using Vectorette PCR‐based nonradioactive transposable element display

Transposable element (TE) display is a method exhibiting the insertion site variations of TE, serving for multiple dominant markers. We report an improved TE display method evaluated by testing inheritance pattern of the TE insertion sites in two different piggyBac‐like elements in a lepidopteran insect tobacco budworm. The specificity of the polymerase chain reaction (PCR)‐based method was confirmed by sequencing randomly chosen a total of 15 bands all revealing the junctions between TE‐end and the flanking sequence. The improved method removes the steps in the conventional TE display method using radiolabelled primers and running denaturing gel, saving time and costs.     

Bergmann's idiosyncratic rule: a role for fecundity selection?

The negative relationship between temperature and geographical variation in body size, or Bergmann's rule, is among the most thoroughly studied ecogeographical rules, yet the pattern and process underlying it remain controversial. Bergmann's original observations were of body size clines among endotherms, but in the last 50 years there has been increasing recognition that both Bergmann's rule and its reverse occur in many ectotherm taxa. A new study of syngnathid fish by Wilson (2009 ) in this issue of Molecular Ecology sheds light on intriguing alternative mechanisms that may explain variation in the direction of body size clines across taxa. Wilson shows that Bergmann's rule is found in pipefish of the genus Syngnathus , but not in seahorses of the genus Hippocampus . His results suggest that polygamy in pipefish allows fecundity selection to favour large size at low temperatures, compensating for increases in brooding time.     

Spatio-temporal variation in the strength and mode of selection acting on major histocompatibility complex diversity in water vole (Arvicola terrestris) metapopulations

Patterns of spatio-temporal genetic variation at a class II major histocompatibility complex (MHC) locus and multiple microsatellite loci were analysed within and between three water vole metapopulations in Scotland, UK. Comparisons of MHC and microsatellite spatial genetic differentiation, based on standardised tests between two demographically asynchronous zones within a metapopulation, suggested that spatial MHC variation was affected by balancing selection, directional selection and random genetic drift, but that the relative effects of these microevolutionary forces vary temporally. At the metapopulation level, between-year differentiation for MHC loci was significantly correlated with that of microsatellites, signifying that neutral factors such as migration and drift were primarily responsible for overall temporal genetic change at the metapopulation scale. Between metapopulations, patterns of genetic differentiation implied that, at large spatial scales, MHC variation was primarily affected by directional selection and drift. Levels of MHC heterozygosity in excess of Hardy–Weinberg expectations were consistent with overdominant balancing selection operating on MHC variation within metapopulations. However, this effect was not constant among all samples, indicating temporal variation in the strength of selection relative to other factors. The results highlight the benefit of contrasting variation at MHC with neutral markers to separate the effects of stochastic and deterministic microevolutionary forces, and add to a growing body of evidence showing that the mode and relative strength of selection acting on MHC diversity varies both spatially and temporally.     

Comparative anatomy and phylogenetic distribution of the mammalian cecal appendix

A recently improved understanding of gut immunity has merged with current thinking in biological and medical science, pointing to an apparent function of the mammalian cecal appendix as a safe‐house for symbiotic gut microbes, preserving the flora during times of gastrointestinal infection in societies without modern medicine. This function is potentially a selective force for the evolution and maintenance of the appendix, and provides an impetus for reassessment of the evolution of the appendix. A comparative anatomical approach reveals three apparent morphotypes of the cecal appendix, as well as appendix‐like structures in some species that lack a true cecal appendix. Cladistic analyses indicate that the appendix has evolved independently at least twice (at least once in diprotodont marsupials and at least once in Euarchontoglires), shows a highly significant (P < 0.0001) phylogenetic signal in its distribution, and has been maintained in mammalian evolution for 80 million years or longer.     

The importance of ant-rich habitats for the persistence of the Wryneck Jynx torquilla on farmland

The frequency of territory occupancy is a good indicator of territory quality. We studied territory occupancy in a Swiss population of the Wryneck Jynx torquilla , a declining farmland woodpecker, with the aim of identifying key habitat features for conservation management. Both static and dynamic approaches were applied using data on nest-site occupancy of 100 territories from six successive years. The static approach models the probability of territory occupancy; the dynamic approach estimates territory colonization and extinction. Frequently occupied territories were settled earlier in the season, suggesting that they may be of better quality, and birds settling in these territories had higher breeding success. Probability of territory occupancy increased with the area of old pear orchards and decreased with the area of vegetable cultivation. Both the area of old pear orchards and the presence of conspecifics within a territory were positively related to territory colonization, whereas territory extinction was negatively related to habitat heterogeneity. Old pear orchards were characterized by having both the highest density of ant nests and the greatest amount of bare ground. The latter is likely to facilitate access to ant prey. To ensure persistence of Wryneck populations in farmland, heterogeneous habitat matrices with high ant nest density and bare ground should be promoted. Finally, provision of artificial nesting cavities is likely to enhance territory occupancy. Providing that these key resources are present, Wrynecks are likely to persist even in intensively farmed areas.     

Facilitation and interference among three predators affect their consumption of a stream-dwelling mayfly

1. We experimentally tested if a multiplicative risk model accurately predicted the consumption of a common mayfly at risk of predation from three predator species in New Zealand streams. Deviations between model predictions and experimental observations were interpreted as indicators of ecologically important interactions between predators. 2. The predators included a drift‐feeding fish [brown trout (T), Salmo trutta], a benthivorous fish [galaxiid (G), koaro, Galaxias brevipennis] and a benthic predatory stonefly (S; Stenoperla sp.) with Deleatidium sp. mayflies as prey. Eight treatments with all predator species combinations and a predator‐free control were used. Experiments were performed in aquaria with cobbles as predator refuges for mayflies and we measured the proportion of prey consumed after 6 h for both day and night trials. 3. Trout consumed a higher proportion of prey than other predators. For the two predator treatments we found less than expected prey consumption in the galaxiid + trout treatment (G + T) for both day and night trials, whereas a higher than expected proportion of prey was consumed during night time in the stonefly + trout (S + T) treatment. 4. The results indicate interference (G + T) and facilitation (S + T) between predators depending on predator identity and time of day. Thus, to make accurate predictions of interspecific interactions, it is necessary to consider the ecology of individual species and how differences influence the direction and magnitude of interactions.     

Seasonal dynamics of macrophytes and phytoplankton in shallow lakes: a eutrophication‐driven pathway from plants to plankton?

1. Seasonal relationships between macrophyte and phytoplankton populations may alter considerably as lakes undergo eutrophication. Understanding of these changes may be key to the interpretation of ecological processes operating over longer (decadal‐centennial) timescales. 2. We explore the seasonal dynamics of macrophytes (measured twice in June and August) and phytoplankton (measured monthly May–September) populations in 39 shallow lakes (29 in the U.K. and 10 in Denmark) covering broad gradients for nutrients and plant abundance. 3. Three site groups were identified based on macrophyte seasonality; 16 lakes where macrophyte abundance was perennially low and the water generally turbid (‘turbid lakes’); 7 where macrophyte abundance was high in June but low in August (‘crashing’ lakes); and 12 where macrophyte abundance was high in both June and August (‘stable’ lakes). The seasonal behaviour of the crashing and turbid lakes was extremely similar with a consistent increase in nutrient concentrations and chlorophyll‐a over May–September. By contrast in the stable lakes, seasonal changes were dampened with chlorophyll‐a consistently low (<10–15 μg L^?1) over the entire summer. The crashing lakes were dominated by one or a combination of Potamogeton pusillus, Potamogeton pectinatus and Zannichellia palustris, whereas Ceratophyllum demersum and Chara spp. were more abundant in the stable lakes. 4. A long‐term loss of macrophyte species diversity has occurred in many shallow lakes affected by eutrophication. One common pathway is from a species‐rich plant community with charophytes to a species‐poor community dominated by P. pusillus, P. pectinatus and Z. palustris. Such compositional changes may often be accompanied by a substantial reduction in the seasonal duration of plant dominance and a greater tendency for incursions by phytoplankton. We hypothesise a slow‐enacting (10–100 s years) feedback loop in nutrient‐enriched shallow lakes whereby increases in algal abundance are associated with losses of macrophyte species and hence different plant seasonal strategies. In turn such changes may favour increased phytoplankton production thus placing further pressure on remaining macrophytes. This study blurs the distinction between so‐called turbid phytoplankton‐dominated and clear plant‐dominated shallow lakes and suggests that plant loss from them may be a gradual process.     

Advances in introgression technologies for precision breeding within the Lolium - Festuca complex

The anticipated complexity of multifunctional grasslands with environment‐friendly and sustainable management practices demands better understanding of traits, their interactions, and their genetic control. Intergeneric hybrids between closely related Lolium and Festuca species are being used to broaden the gene pool and provide the plant breeder with options to combine complementary traits aimed at high quality but more robust grass varieties for the future. New techniques in introgression mapping provide opportunities for precision breeding whereby desirable gene combinations transferred from one species into another are selected preferentially, with the exclusion of deleterious alien genes. The close homology between genomes of Lolium and Festuca species allows high levels of chromosome pairing and recombination. Using genomic in situ hybridisation (GISH) on Lolium/Festuca hybrids and their derivatives, recombination between Lolium and Festuca chromosomes is observed at any point along the chromosome. The system provides unlimited access to any combination of Lolium and Festuca DNA sequence. Moreover, genes transferred between homoeologous chromosome sites are expected to function normally at their new locations. Alien chromosome segments may be reduced in size by further recombination events thereby reducing linkage drag. Molecular markers such as AFLPs, SSRs, SNPs, or RFLPs are being targeted to genes of interest to allow their selection through different generations in plant breeding programmes. Relatively simple PCR‐based marker systems are used for specific traits as breeders' toolkits in plant breeding programmes.